1. Field of the Invention
The present invention relates to lighting fixtures for indirect room illumination through reflection of most of the fixture""s light off of the room""s ceiling, but also having a small, aesthetically pleasing downward component. More particularly, this invention relates to indirect office environment fluorescent tube lighting fixtures which are mountable close to the ceiling while providing uniform illumination of the ceiling and a high efficiency fixture.
2. Description of Prior Art
With the recent proliferation of Video Display Terminals (VDTS) in the office environment, lighting designers have identified high contrast overhead lighting as a source of glare and reflection on VDT screens. Such glare and reflection is an undesirable effect which impacts worker comfort and productivity. Thus, the need has arisen for efficient low contrast illumination of the work environment.
Indirect fluorescent tube overhead lighting has been determined to be the most efficient means of illuminating a large office environment, while providing low contrast illumination of the work area. Such lighting is accomplished by positioning fluorescent tube fixtures below the plane of the ceiling and directing nearly all of the light upward toward the ceiling. The light is then reflected off of the ceiling downward toward the room. Uniform illumination of the ceiling will provide low contrast lighting.
Additionally, designers have found that eliminating glare does not in itself result in a pleasant environment. An appropriate perceived brightness has been found to be necessary to create comfort and a sense of well-being. Thus, lighting designers have recently indicated an preference for aesthetic, low illumination of the fixture housing when viewed from the working area of the room.
Indirect fluorescent tube overhead lighting fixtures of the current art often must be suspended a significant distance below the plane of the ceiling in order to obtain a uniform light pattern while maintaining an efficient light fixture. This phenomena is due to the fact that the optical reflector systems in such fixtures of the current art distribute light output toward the ceiling at high angles (angles much greater than 105 degrees as measured from nadir). A problem, however, with mounting the fixtures a significant distance below the ceiling is that a xe2x80x98false ceilingxe2x80x99 impression is created by the rows of fixtures needed to illuminate a large work area. For instance, when looking out across a room containing multiple rows of suspended fixtures, the rows of fixtures themselves form a plane of fixtures at the suspension distance below the plane of the ceiling. In a room with 9 or 10 foot ceilings, a suspension distance of 24 to 36 inches will create an uncomfortably low false ceiling.
In order to address this problem, the light fixtures must be mounted closer to the ceiling. However, mounting fixtures with high angle light distribution close to the ceiling necessitates that the rows of fixtures be located closer to one another in order to achieve uniform illumination of the ceiling, increasing the number of fixture and the cost to illuminate the room.
Previous efforts to design fixtures with lower angles of light distribution have resulted in less efficient fixtures.
Additionally, efforts to design fixtures having illuminated housings when viewed from below have also resulted in less efficient fixtures.
It is an object of the present invention to provide an indirect fluorescent tube overhead lighting fixture with an optical system distributing light at low angles while maintaining a high efficiency.
It is a further object of the present invention to provide an indirect fluorescent tube overhead lighting fixture having an illuminated housing when viewed from below while maintaining a high efficiency.
These and other objects are achieved through the use of an optical system having a tubular lamp, a parabolic reflector assembly under the lamp, a pair of kick reflector assemblies on either side of the lamp and spaced from the parabolic reflector assembly creating openings, and a housing having translucent areas in optical communication with the lamp through the openings.
The parabolic reflector assembly may have a pair of substantially parabolic shaped reflectors joined to form an apex in a vertical plane defined by the apex and the longitudinal axis of the tubular lamp. The parabolic shaped reflectors may be symmetric about the vertical plane. The parabolic reflectors may each have a proximate edge along the apex and a distal edge opposite to the proximate edge. Further, the parabolic reflector distal edges and the tubular lamp longitudinal axis may be positioned to define planes intersecting the vertical plane at substantially 60 degrees on either side of the vertical plane.
The substantially parabolic shaped reflectors may also be comprised or approximated by at least two arc segments.
Each kick reflector assembly may be symmetric with the other about the lamp axis vertical plane, and may have a substantially vertical section which lies in a plane which is upwardly and outwardly diverging from the lamp axis vertical plane. Additionally, each kick reflector assembly may further have a horizontal section extending inwardly from the substantially vertical section and having a proximate edge located along the opening between the kick reflector assembly and the parabolic reflector assembly. Further, the kick reflector assembly horizontal section proximate edges and the tubular lamp longitudinal axis may be positioned to define planes intersecting the vertical plane at substantially 73 degrees on either side of the vertical plane.